The present invention relates to reducing gas pulsations and consequently induced noise during the operation of rotary lobe positive displacement blowers or reciprocating compressors of the type used in non-cryogenic gas separation systems.
Non-cryogenic gas separation processes, especially adsorptive processes, are used to separate various components from a gaseous mixture, e.g. oxygen from air. Two major adsorptive processes are currently in use. These are pressure swing adsorption (PSA) and vacuum swing adsorption (VSA). Pressure swing adsorption is carried out with the adsorption (feed) step at pressures much higher than ambient and adsorbent regeneration at pressures close to ambient. In the vacuum swing adsorption (VSA) processes, adsorption is carried out at pressure close to ambient and the adsorbent regeneration is carried out at sub-atmospheric pressure levels. U.S. Pat. No. 4,561,865 illustrates a prior art pressure swing adsorption process and U.S. Pat. No. 4,813,977 illustrates a prior art vacuum swing adsorption process.
Conventional PSA and VSA processes employ positive displacement compressors and blowers for either fluid compression or exhaustion in the adsorbent vessel. A positive displacement compressor or blower ingests a fixed volume of gas, compresses the gas to higher pressure, and discharges the compressed gas into a discharge pipe, conduit or chamber. The flow of gas into and out of the compressor or blower is non-steady due to the nature of the machine taking in fixed volumes of gas at a given frequency. This action creates pressure fluctuations in the inlet and discharge pipes or conduits connected to the compressor or blower. Pressure fluctuations of this type are commonly referred to as gas pulsations.
Gas pulsations can cause problems within the gas separation system such as piping vibrations, air and gas filter distress, noise, adsorbent bed agitation, and water separator inefficiency where the positive displacement apparatus is of the water injected type. Gas pulsations from a positive displacement apparatus (blower or compressor) can be in the range of 10 to 20 percent of the absolute line pressure without some form of pressure pulsation reduction. The gas pulsations act upon any surface within the gas flow path and thus generate a force on such surfaces equal to pressure pulsation amplitude times the surface area.
Piping systems experience shaking forces when gas pulsations act upon flow impingement surfaces such as pipe elbows, tees and associated vessels. The gas pulsations can also produce noise by causing the pipe and vessel surfaces to vibrate and radiate sound pressure waves into the atmosphere much like the diaphragm of a drum. The gas pulsations act upon filters and adsorber beds causing them to vibrate and eventually can cause damage to the filters and beds. In some applications positive displacement blowers employ water injection into the blower to act as a sealant and a coolant. The water must be separated from the gas stream in the blower discharge flow. Gas pulsations adversely effect good separation where smooth flow and low velocity are important parameters for good water-gas separation. In order to achieve good water separation a large separation vessel is required. Large separation vessels contain large surfaces which in turn can radiate noise caused by any gas pulsations within the separator. Therefore, it is desirable to eliminate harmful gas pulsations from the system prior to the gas containing water entering into the separator.
Gas pulsations can be attenuated and or minimized by using surge bottles, resonator bottles, choke tubes, orifices, or diffusers. However, these devices have not been effective in gas pulsation and induced noise reduction with water injected positive displacement blowers or compressors.
U.S. Pat. Nos. 4,927,342 and 5,203,679 disclose use of resonators that are applied to attenuating noise from rotary compressors.
U.S. Pat. No. 4,294,330 discloses use of a muffler device for use with pneumatic devices such as a pneumatic drill.
U.S. Pat. No. 5,040,495 discloses use of a resonator applied to an internal combustion engine.
U.S. Pat. No. 4,162,904 discloses a prior art silencer/separator for use with high velocity gas streams for separating entrained liquid from the gas.
A Russian Patent SU 1359552 A1 discloses suppression of blower pulsations in a power-plant system.